Systems and methods for selective electrosurgical treatment of body structures

ABSTRACT

The present invention provides systems and methods for selectively applying electrical energy to a target location within a patient&#39;s. The present invention positions an electrosurgical instrument, such as a probe or catheter, in close proximity to a first body structure adjacent to a second body structure so that one or more electrode terminal(s) are brought into at least partial contact or close proximity with the first and second body structures. High frequency voltage is then applied between the electrode terminal(s) and one or more return electrode(s) to cut, remove, ablate, contract, coagulate, vaporize, desiccate or otherwise modify the first body structure without clinically damaging the second body structure. The first body structure is typically soft tissue, such as sinus, mucosal, spinal, or brain tissue, and the second body structure typically comprises a structure either having different electrical or molecular properties than soft tissue, such as bone, cartilage, adipose tissue, nerves and the like. The present invention provides a method for automatically discriminating between the two body structures such that the soft tissue is removed or otherwise modified, while the second structure (e.g., a nerve) is left relatively unaffected by the procedure.

RELATED APPLICATIONS

The present invention is a continuation-in-part of U.S. patentapplication Ser. No. 08/990,374 entitled “Systems and Methods forElectrosurgical Endoscopic Sinus Surgery, filed on Dec. 15, 1997 nowU.S. Pat. No. 6,109,268, which is a continuation-in-part of U.S. patentapplication Ser. No. 08/485,219, filed on Jun. 7, 1995 now U.S. Pat. No.5,697,281, the complete disclosures of which are incorporated herein byreference for all purposes. The invention is also a continuation-in-partof U.S. patent application entitled “Systems and Methods forElectrosurgical Spine Surgery,” filed on Feb. 20, 1998, the completedisclosure of which is incorporated herein by reference for allpurposes.

This application is also related to commonly assigned U.S. patentapplication Ser. No. 08/942,580 entitled “Systems and Methods forElectrosurgical Tissue Contraction”, filed on Oct. 2, 1997, ProvisionalPatent Application Nos. 60/062,996 and 60/062,997, non-provisional U.S.patent application Ser. No. 08/970,239 entitled “Electrosurgical Systemsand Methods for Treating the Spine”, filed Nov. 14, 1997, and Ser. No.08/977,845 entitled “Systems and Methods for ElectrosurgicalDermatological Treatment”, filed on Nov. 25, 1997, U.S. application Ser.No. 08/753,227, filed on Nov. 22, 1996, and PCT InternationalApplication, U.S. National Phase Serial No. PCT/US94/05168, filed on May10, 1994, now U.S. Pat. No. 5,697,909, which was a continuation-in-partof application Ser. No. 08/059,681, filed on May 10, 1993, which was acontinuation-in-part of application Ser. No. 07/958,977, filed on Oct.9, 1992 which was a continuation-in-part of application Ser. No.07/817,575, filed on Jan. 7, 1992, the complete disclosures of which areincorporated herein by reference for all purposes. The present inventionis also related to commonly assigned U.S. Pat. No. 5,683,366, filed Nov.22, 1995, and U.S. Pat. No. 5,697,536, filed on Nov. 18, 1996, thecomplete disclosures of which are incorporated herein by reference forall purposes.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of electrosurgery,and more particularly to surgical devices and methods which employ highfrequency electrical energy to treat tissue in regions of the bodyadjacent to nerves or other sensitive body structures, such as the headand neck, the spine, the brain and the like.

Many surgical procedures involve the treatment and/or removal of softtissue closely adjacent to other non-target body structures, such asnerves, bone or cartilage (e.g., articular cartilage). One of the majordifficulties with these procedures is discriminating between the targetsoft tissue and the non-target body structure, and then being capable ofremoving or otherwise modifying the soft tissue without damaging thenon-target structure. Particularly troublesome are those surgicalprocedures which require the surgeon to remove tissue adjacent to nerves(the cordlike structures which convey impulses between a part of thecentral nervous system and a region of the body).

Many surgical procedures require the manipulation of surgicalinstruments in and around important nerves in the body. For example,surgical procedures within the nasal cavity (e.g., FESS procedures)often require the surgeon to remove polyps, turbinates or other sinustissue adjacent to the optic or olfactory nerves, which are the centralprocesses for sight and smell. Surgical procedures within the mouthoften involves ablation or contraction of tissue (e.g., in the tongue oruvula) near the hypoglossal nerve, which controls movements of thetongue. Similarly, in spinal procedures (e.g., treatment of herniateddiscs or spinal fusion), the surgeon must often remove or modify tissueclosely adjacent to the spinal nerves near their roots at the spinalcord. One of the significant problems with these procedures is thatconventional surgical instruments generally do not differentiate betweenthe target tissue and the surrounding nerves, which may result in nerveinjury of impairment of nerve function. Nerve injury can lead to muscleparalysis, pain, exaggerated reflexes, loss of bladder control, impairedcough reflexes, spasticity and other conditions. Moreover, the neuronswithin some nerves typically do not regenerate after injury.

In the past several years, powered instrumentation, such asmicrodebrider devices and lasers, has been used to treat tissue invarious procedures, such as removing polyps or other swollen tissue infunctional endoscopic sinus surgery. Microdebriders are disposablemotorized cutters having a rotating shaft with a serrated distal tip forcutting and resecting tissue. The handle of the microdebrider istypically hollow, and it accommodates a small vacuum, which serves toaspirate debris. In this procedure, the distal tip of the shaft isdelivered to the target site, and an external motor rotates the shaftand the serrated tip, allowing the tip to cut tissue at the target site,such as sinus tissue, spinal tissue, or the like. While microdebridershave been promising, they are not very precise, and it is oftendifficult, during the procedure, to differentiate between the targettissue, and other neighboring body structures, such as cartilage, boneor nerves. Thus, the surgeon must be extremely careful to minimizedamage to the cartilage and bone at the target site, and to avoiddamaging the nerves that extend through the target site.

Lasers were initially considered ideal for many surgical proceduresbecause lasers ablate or vaporize tissue with heat, which also acts tocauterize and seal the small blood vessels in the tissue. Unfortunately,lasers are both expensive and somewhat tedious to use in theseprocedures. Another disadvantage with lasers is the difficulty injudging the depth of tissue ablation. Since the surgeon generally pointsand shoots the laser without contacting the tissue, he or she does notreceive any tactile feedback to judge how deeply the laser is cutting.Because healthy tissue, cartilage, bone and/or nerves often lie withinclose proximity of the target tissue, it is essential to maintain aminimum depth of tissue damage, which cannot always be ensured with alaser.

Recently, RF energy has been used to remove or otherwise treat tissue inopen and endoscopic procedures. This procedure typically involves theuse of a monopolar electrode that directs RF current into the targettissue to desiccate or destroy tissue in the tongue. Of course, suchmonopolar devices suffer from the disadvantage that the electric currentwill flow through undefined paths in the patient's body, therebyincreasing the risk of unwanted electrical stimulation to portions ofthe patient's body. In addition, since the defined path through thepatient's body has a relatively high impedance (because of the largedistance or resistivity of the patient's body), large voltagedifferences must typically be applied between the return and activeelectrodes in order to generate a current suitable for ablation orcutting of the target tissue. This current, however, may inadvertentlyflow along body paths having less impedance than the defined electricalpath, which will substantially increase the current flowing throughthese paths, possibly causing damage to or destroying surrounding tissueor neighboring peripheral nerves.

SUMMARY OF THE INVENTION

The present invention provides systems, apparatus and methods forselectively applying electrical energy to structures in regions of thepatient's body adjacent to non-target body structures, such as nerves,cartilage and bone. The systems and methods of the present invention areparticularly useful for ablation, resection, contraction and hemostatisof soft tissue that is closely adjacent to nerves, such as tissue withinthe head and neck, the spine, the brain and the like.

Methods of the present invention comprise positioning an electrosurgicalinstrument, such as a probe or catheter, in close proximity to a firstbody structure adjacent to a second body structure so that one or moreelectrode terminal(s) are brought into at least partial contact or closeproximity with the first and second body structures. High frequencyvoltage is then applied between the electrode terminal(s) and one ormore return electrode(s) to cut, remove, ablate, contract, coagulate,vaporize, desiccate or otherwise modify the first body structure withoutdamaging the second body structure. The first body structure istypically soft tissue, such as sinus, mucosal, spinal, or brain tissue,and the second body structure typically comprises a structure eitherhaving different electrical or molecular properties than soft tissue,such as bone, cartilage, adipose tissue, nerves and the like. Thepresent invention provides a method for automatically discriminatingbetween the two body structures such that the soft tissue is removed orotherwise modified, while the second structure is left relativelyunaffected by the procedure.

In one aspect of the invention, a method is provided for removing orablating soft tissue that is adjacent to a nerve structure, such asswollen nasal tissue within the sinuses, disc tissue within the spine,tumor tissue within the brain and the like. In this method, one or moreelectrode terminal(s) are positioned adjacent to the target tissue,either endoscopically, transluminally, or directly in an open procedure.An electrically conductive fluid, such as isotonic saline, is deliveredto the target site to substantially surround the electrode terminal(s)with the fluid. Alternatively, a more viscous fluid, such as anelectrically conductive gel, may be applied to the target site such thatthe electrode terminal(s) are submerged within the gel during theprocedure. In both embodiments, high frequency voltage is appliedbetween the electrode terminal(s) and one or more return electrode(s) toremove at least a portion of the tissue. According to the presentinvention, the electrical energy is selectively applied to soft tissueto ablate this tissue, while minimizing energy delivery to the adjacentnerves. In particular, applicant has found that the present invention iscapable of completely removing soft tissue closely adjacent to nerveswithout causing nerve function impairment or any significant changes tothe tissue in nerve fibers or the surrounding epineurium.

In one embodiment, the soft tissue is removed by molecular dissociationor disintegration processes. In this embodiment, the high frequencyvoltage applied to the electrode terminal(s) is sufficient to vaporizean electrically conductive fluid (e.g., gel or saline) between theelectrode terminal(s) and the soft tissue. Within the vaporized fluid, aionized plasma is formed and charged particles (e.g., electrons) areaccelerated towards the tissue to cause the molecular breakdown ordisintegration of several cell layers of the tissue. This moleculardissociation is accompanied by the volumetric removal of the tissue. Theshort range of the accelerated charged particles within the plasma layerconfines the molecular dissociation process to the surface layer tominimize damage and necrosis to the underlying tissue. This process canbe precisely controlled to effect the volumetric removal of tissue asthin as 10 to 150 microns with minimal heating of, or damage to,surrounding or underlying tissue structures. The small depths ofcollateral tissue damage provided by the present invention allows thesurgeon to remove tissue close to a nerve without causing collateraldamage to the nerve fibers. A more complete description of thisphenomena is described in commonly assigned U.S. Pat. No. 5,683,366, thecomplete disclosure of which is incorporated herein by reference

In another embodiment, systems and methods are provided fordistinguishing between the fatty tissue (e.g., adipose tissue)immediately surrounding nerve fibers and the normal tissue that is to beremoved during the procedure. Nerves usually comprise a connectivetissue sheath, or epineurium, enclosing the bundles of nerve fibers toprotect these nerve fibers. This protective tissue sheath comprises afatty tissue (e.g., adipose tissue) having substantially differentelectrical properties than the normal target tissue. The system of thepresent invention measures the electrical properties of the tissue atthe tip of the probe with one or more electrode terminal(s). Theseelectrical properties may include electrical conductivity at one,several or a range of frequencies (e.g., in the range from 1 kHz to 100MHz), dielectric constant, capacitance or combinations of these. In thisembodiment, an audible signal may be produced when the sensingelectrode(s) at the tip of the probe detects the fatty tissuesurrounding a nerve, or direct feedback control can be provided to onlysupply power to the electrode terminal(s) either individually or to thecomplete array of electrodes, if and when the tissue encountered at thetip or working end of the probe is normal tissue based on the measuredelectrical properties.

In yet another embodiment, applicant has discovered that the mechanismsof the present invention can be manipulated to ablate or remove certaintissue structures, while having little effect on other body structures.As discussed above, the present invention employs a technique ofvaporizing electrically conductive fluid to form a plasma layer orpocket around the electrode terminal(s), and then inducing the dischargeof energy from this plasma or vapor layer to break the molecular bondsof the tissue structure. Energy evolved by the energetic electrons(e.g., 4 to 5 eV) can subsequently bombard a molecule and break itsbonds, dissociating a molecule into free radicals, which then combineinto final gaseous or liquid species. The energy evolved by theenergetic electrons may be varied by adjusting a variety of factors,such as: the number of electrode terminals; electrode size and spacing;electrode surface area; asperities and sharp edges on the electrodesurfaces; electrode materials; applied voltage and power; currentlimiting means, such as inductors; electrical conductivity of the fluidin contact with the electrodes; density of the fluid; and other factors.Accordingly, these factors can be manipulated to control the energylevel of the excited electrons. Since different tissue structures havedifferent molecular bonds, the present invention can be configured tobreak the molecular bonds of certain tissue, while having too low anenergy to break the molecular bonds of other tissue. For example, fattytissue, (e.g., adipose) tissue has double bonds that require asubstantially higher energy level than 4 to 5 eV to break. In anexemplary embodiment, the present invention does not ablate or removesuch fatty tissue.

In another aspect of the invention, a method includes positioning one ormore electrode terminal(s) in close proximity to a target site adjacentto a nerve structure. High frequency voltage is applied to the electrodeterminal(s) to elevate the temperature of collagen fibers within thetissue at the target site from body temperature (about 37° C.) to atissue temperature in the range of about 45° C. to 90° C., usually about60° C. to 70° C., to substantially irreversibly contract these collagenfibers without damaging the nerve. In a preferred embodiment, anelectrically conducting fluid is provided between the electrodeterminal(s) and one or more return electrode(s) positioned proximal tothe electrode terminal(s) to provide a current flow path from theelectrode terminal(s) away from the tissue to the return electrode(s).

The current flow path may be generated by directing an electricallyconducting fluid along a fluid path past the return electrode and to thetarget site, or by locating a viscous electrically conducting fluid,such as a gel, at the target site, and submersing the electrodeterminal(s) and the return electrode(s) within the conductive gel. Thecollagen fibers may be heated either by passing the electric currentthrough the tissue to a selected depth before the current returns to thereturn electrode(s) and/or by heating the electrically conducting fluidand generating a jet or plume of heated fluid, which is directed towardsthe target tissue. In the latter embodiment, the electric current maynot pass into the tissue at all. In both embodiments, the heated fluidand/or the electric current elevates the temperature of the collagensufficiently to cause hydrothermal shrinkage of the collagen fibers.

The contraction of collagen tissue is particularly useful in proceduresfor treating obstructive sleep disorders, such as snoring or sleepapnea, and for treating herniated discs by shrinking the nucleuspulposis of the herniated disc. In the former procedure, one or moreelectrode terminal(s) are introduced into the patient's mouth, andpositioned adjacent the target tissue, selected portions of the tongue,tonsils, soft palate tissues (e.g., the uvula), hard tissue and mucosaltissue. An endoscope or other type of viewing device, may also beintroduced, or partially introduced, into the mouth to allow the surgeonto view the procedure (the viewing device may be integral with, orseparate from, the electrosurgical probe). Electrically conductive fluidis applied as described above, and high frequency voltage is applied tothe electrode terminal(s) and one or more return electrode(s) to, forexample, ablate or shrink sections of the uvula without causing unwantednerve damage to nerves extending under and around the selected sectionsof tissue.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a bundle of nerve fibers enclosed within an outerprotective sheath or epineurium;

FIG. 1B illustrates a single nerve fiber;

FIG. 2 is a perspective view of an electrosurgical system incorporatinga power supply and an electrosurgical probe for tissue ablation,resection, incision, contraction and for vessel hemostasis according tothe present invention;

FIG. 3 is a side view of an electrosurgical probe according to thepresent invention;

FIG. 4A is a cross sectional view of the electrosurgical probe of FIG.1;

FIG. 4B is an end view of the probe of FIG. 2

FIG. 5 is an exploded view of a proximal portion of the electrosurgicalprobe;

FIGS. 6-11(A-C) are end views of alternative embodiments of the probe ofFIG. 2, incorporating aspiration electrode(s);

FIG. 12 illustrates an endoscopic sinus surgery procedure, wherein anendoscope is delivered through a nasal passage to view a surgical sitewithin the nasal cavity of the patient;

FIG. 13 illustrates an endoscopic sinus surgery procedure with one ofthe probes described above according to the present invention;

FIGS. 14A and 14B illustrate a detailed view of the sinus surgeryprocedure, illustrating ablation of tissue according to the presentinvention;

FIG. 15 illustrates a procedure for treating obstructive sleepdisorders, such as sleep apnea, according to the present invention;

FIGS. 16-19 illustrate a method of performing a microendoscopicdiscectomy according to the principles of the present invention; and

FIG. 20 is a schematic of another electrosurgical system fordiscriminating between body structures having different electricalproperties, illustrating a plurality of inductors functioning as currentlimiting elements to a plurality of electrodes on the distal end of anelectrosurgical probe.

DESCRIPTION OF SPECIFIC EMBODIMENTS

The present invention provides systems and methods for selectivelyapplying electrical energy to a target location within or on a patient'sbody, particularly including tissue in the head and neck, such as theear, mouth, pharynx, larynx, esophagus, nasal cavity and sinuses. Thehead and neck procedures may be performed through the mouth or noseusing speculae or gags, or using endoscopic techniques, such asfunctional endoscopic sinus surgery (FESS). These procedures may includethe removal of swollen tissue, chronically-diseased inflamed andhypertrophic mucus linings, polyps, turbinates and/or neoplasms from thevarious anatomical sinuses of the skull, the turbinates and nasalpassages, in the tonsil, adenoid, epi-glottic and supra-glottic regions,and salivary glands, submucus resection of the nasal septum, excision ofdiseased tissue and the like. In other procedures, the present inventionmay be useful for collagen shrinkage, ablation and/or hemostasis inprocedures for treating swollen tissue (e.g., turbinates) or snoring andobstructive sleep apnea (e.g., soft palate, such as the uvula, ortongue/pharynx stiffening, and midline glossectomies), for gross tissueremoval, such as tonsillectomies, adenoidectomies, tracheal stenosis andvocal cord polyps and lesions, or for the resection or ablation offacial tumors or tumors within the mouth and pharynx, such asglossectomies, laryngectomies, acoustic neuroma procedures and nasalablation procedures. In addition, the present invention is useful forprocedures within the ear, such as stapedotomies, tympanostomies or thelike.

The present invention may also be useful for treating tissue or otherbody structures in the brain or spine. These procedures include tumorremoval, laminectomy/disketomy procedures for treating herniated disks,decompressive laminectomy for stenosis in the lumbosacral and cervicalspine, medial facetectomy, posterior lumbosacral and cervical spinefusions, treatment of scoliosis associated with vertebral disease,foraminotomies to remove the roof of the intervertebral foramina torelieve nerve root compression and anterior cervical and lumbardiskectomies. These procedures may be performed through open procedures,or using minimally invasive techniques, such as thoracoscopy,arthroscopy, laparascopy or the like.

In the present invention, high frequency (RF) electrical energy isapplied to one or more electrode terminals in the presence ofelectrically conductive fluid to remove and/or modify the structure oftissue structures. Depending on the specific procedure, the presentinvention may be used to: (1) volumetrically remove tissue, bone,ligament or cartilage (i.e., ablate or effect molecular dissociation ofthe body structure); (2) cut or resect tissue or other body structures;(3) shrink or contract collagen connective tissue; and/or (4) coagulatesevered blood vessels.

In some procedures, e.g., soft palate or tongue/pharynx stiffening orshrinkage of the nucleus pulposis in herniated discs, it is desired toshrink or contract collagen connective tissue at the target site. Inthese procedures, the RF energy heats the tissue directly by virtue ofthe electrical current flow therethrough, and/or indirectly through theexposure of the tissue to fluid heated by RF energy, to elevate thetissue temperature from normal body temperatures (e.g., 37° C.) totemperatures in the range of 45° C. to 90° C., preferably in the rangefrom about 60° C. to 70° C. Thermal shrinkage of collagen fibers occurswithin a small temperature range which, for mammalian collagen is in therange from 60° C. to 70° C. (Deak, G., et al., “The Thermal ShrinkageProcess of Collagen Fibres as Revealed by Polarization Optical Analysisof Topooptical Staining Reactions,” Acta Morphologica Acad. Sci. ofHungary, Vol. 15(2), pp 195-208, 1967). Collagen fibers typicallyundergo thermal shrinkage in the range of 60° C. to about 70° C.Previously reported research has attributed thermal shrinkage ofcollagen to the cleaving of the internal stabilizing cross-linkageswithin the collagen matrix (Deak, ibid). It has also been reported thatwhen the collagen temperature is increased above 70° C., the collagenmatrix begins to relax again and the shrinkage effect is reversedresulting in no net shrinkage (Allain, J. C., et al., “IsometricTensions Developed During the Hydrothermal Swelling of Rat Skin,”Connective Tissue Research, Vol. 7, pp 127-133, 1980). Consequently, thecontrolled heating of tissue to a precise depth is critical to theachievement of therapeutic collagen shrinkage. A more detaileddescription of collagen shrinkage can be found in U.S. patentapplication No. Unassigned, filed on Oct. 2, 1997, entitled “Systems AndMethods For Electrosurgical Tissue Contraction” (Attorney Docket No.16238-001300).

The preferred depth of heating to effect the shrinkage of collagen inthe heated region (i.e., the depth to which the tissue is elevated totemperatures between 60° C. to 70° C.) generally depends on (1) thethickness of the tissue, (2) the location of nearby structures (e.g.,nerves) that should not be exposed to damaging temperatures, (3) thelocation of the collagen tissue layer within which therapeutic shrinkageis to be effected and/or (4) the volume of contraction desired torelieve pressure on the spinal nerve. The depth of heating is usually inthe range from 0 to 3.5 mm. In the case of collagen within the softpalate, spinal discs or the uvula, the depth of heating is preferably inthe range from about 0.2 to about 2 mm.

In another method of the present invention, the tissue structures arevolumetrically removed or ablated. In this procedure, a high frequencyvoltage difference is applied between one or more electrode terminal(s)and one or more return electrode(s) to develop high electric fieldintensities in the vicinity of the target tissue site. The high electricfield intensities lead to electric field induced molecular breakdown oftarget tissue through molecular dissociation (rather than thermalevaporation or carbonization). Applicant believes that the tissuestructure is volumetrically removed through molecular disintegration oflarger organic molecules into smaller molecules and/or atoms, such ashydrogen, oxides of carbon, hydrocarbons and nitrogen compounds. Thismolecular disintegration completely removes the tissue structure, asopposed to dehydrating the tissue material by the removal of liquidwithin the cells of the tissue, as is typically the case withelectrosurgical desiccation and vaporization.

The high electric field intensities may be generated by applying a highfrequency voltage that is sufficient to vaporize an electricallyconducting fluid over at least a portion of the electrode terminal(s) inthe region between the distal tip of the electrode terminal(s) and thetarget tissue. The electrically conductive fluid may be a gas or liquid,such as isotonic saline, delivered to the target site, or a viscousfluid, such as a gel, that is located at the target site. In the latterembodiment, the electrode terminal(s) are submersed in the electricallyconductive gel during the surgical procedure. Since the vapor layer orvaporized region has a relatively high electrical impedance, itincreases the voltage differential between the electrode terminal tipand the tissue and causes ionization within the vapor layer due to thepresence of an ionizable species (e.g., sodium when isotonic saline isthe electrically conducting fluid). This ionization, under optimalconditions, induces the discharge of energetic electrons and photonsfrom the vapor layer and to the surface of the target tissue. Thisenergy may be in the form of energetic photons (e.g., ultravioletradiation), energetic particles (e.g., electrons) or a combinationthereof. A more detailed description of this cold ablation phenomena,termed Coblation™, can be found in commonly assigned U.S. Pat. No.5,683,366 the complete disclosure of which is incorporated herein byreference.

The present invention applies high frequency (RF) electrical energy inan electrically conducting fluid environment to remove (i.e., resect,cut or ablate) or contract a tissue structure, and to seal transectedvessels within the region of the target tissue. The present invention isparticularly useful for sealing larger arterial vessels, e.g., on theorder of 1 mm or greater. In some embodiments, a high frequency powersupply is provided having an ablation mode, wherein a first voltage isapplied to an electrode terminal sufficient to effect moleculardissociation or disintegration of the tissue, and a coagulation mode,wherein a second, lower voltage is applied to an electrode terminal(either the same or a different electrode) sufficient to achievehemostasis of severed vessels within the tissue. In other embodiments,an electrosurgical probe is provided having one or more coagulationelectrode(s) configured for sealing a severed vessel, such as anarterial vessel, and one or more electrode terminals configured foreither contracting the collagen fibers within the tissue or removing(ablating) the tissue, e.g., by applying sufficient energy to the tissueto effect molecular dissociation. In the latter embodiments, thecoagulation electrode(s) may be configured such that a single voltagecan be applied to coagulate with the coagulation electrode(s), and toablate or contract with the electrode terminal(s). In other embodiments,the power supply is combined with the coagulation probe such that thecoagulation electrode is used when the power supply is in thecoagulation mode (low voltage), and the electrode terminal(s) are usedwhen the power supply is in the ablation mode (higher voltage).

In the method of the present invention, one or more electrode terminalsare brought into close proximity to tissue at a target site, and thepower supply is activated in the ablation mode such that sufficientvoltage is applied between the electrode terminals and the returnelectrode to volumetrically remove the tissue through moleculardissociation, as described below. During this process, vessels withinthe tissue will be severed. Smaller vessels will be automatically sealedwith the system and method of the present invention. Larger vessels, andthose with a higher flow rate, such as arterial vessels, may not beautomatically sealed in the ablation mode. In these cases, the severedvessels may be sealed by activating a control (e.g., a foot pedal) toreduce the voltage of the power supply into the coagulation mode. Inthis mode, the electrode terminals may be pressed against the severedvessel to provide sealing and/or coagulation of the vessel.Alternatively, a coagulation electrode located on the same or adifferent probe may be pressed against the severed vessel. Once thevessel is adequately sealed, the surgeon activates a control (e.g.,another foot pedal) to increase the voltage of the power supply backinto the ablation mode.

The present invention is particularly useful for removing or ablatingtissue around nerves, such as spinal or cranial nerves, e.g., theolfactory nerve on either side of the nasal cavity, the optic nervewithin the optic and cranial canals, the palatine nerve within the nasalcavity, soft palate, uvula and tonsil the spinal cord and thesurrounding dura mater, etc. One of the significant drawbacks with theprior art microdebriders and lasers is that these devices do notdifferentiate between the target tissue and the surrounding nerves orbone. Therefore, the surgeon must be extremely careful during theseprocedures to avoid damage to the bone or nerves within and around thenasal cavity. In the present invention, the Coblation™ process forremoving tissue results in extremely small depths of collateral tissuedamage as discussed above. This allows the surgeon to remove tissueclose to a nerve without causing collateral damage to the nerve fibers.

In addition to the generally precise nature of the novel mechanisms ofthe present invention, applicant has discovered an additional method ofensuring that adjacent nerves are not damaged during tissue removal.According to the present invention, systems and methods are provided fordistinguishing between the fatty tissue immediately surrounding nervefibers and the normal tissue that is to be removed during the procedure.As shown in FIGS. 1A and 1B, nerves 2 usually comprise a connectivetissue sheath, or epineurium 4, enclosing the bundles of nerve fibers 6,each bundle being surrounded by its own sheath of connective tissue (theperineurium) to protect these nerve fibers. The outer protective tissuesheath or epineurium 4 typically comprises a fatty tissue (e.g., adiposetissue) having substantially different electrical properties than thenormal target tissue, such as the turbinates, polyps, mucus tissue orthe like, that are, for example, removed from the nose during sinusprocedures. The system of the present invention measures the electricalproperties of the tissue at the tip of the probe with one or moreelectrode terminal(s). These electrical properties may includeelectrical conductivity at one, several or a range of frequencies (e.g.,in the range from 1 kHz to 100 MHz), dielectric constant, capacitance orcombinations of these. In this embodiment, an audible signal may beproduced when the sensing electrode(s) at the tip of the probe detectsthe fatty tissue 4 surrounding a nerve 6, or direct feedback control canbe provided to only supply power to the electrode terminal(s) eitherindividually or to the complete array of electrodes, if and when thetissue encountered at the tip or working end of the probe is normaltissue based on the measured electrical properties.

In one embodiment, the current limiting elements (discussed in detailabove) are configured such that the electrode terminals will shut downor turn off when the electrical impedance reaches a threshold level.When this threshold level is set to the impedance of the fatty tissue 4surrounding nerves 6, the electrode terminals will shut off wheneverthey come in contact with, or in close proximity to, nerves. Meanwhile,the other electrode terminals, which are in contact with or in closeproximity to nasal tissue, will continue to conduct electric current tothe return electrode. This selective ablation or removal of lowerimpedance tissue in combination with the Coblation™ mechanism of thepresent invention allows the surgeon to precisely remove tissue aroundnerves or bone. Applicant has found that the present invention iscapable of volumetrically removing tissue closely adjacent to nerveswithout impairment the function of the nerves, and without significantlydamaging the tissue of the epineurium.

In addition to the above, applicant has discovered that the Coblation™mechanism of the present invention can be manipulated to ablate orremove certain tissue structures, while having little effect on othertissue structures. As discussed above, the present invention uses atechnique of vaporizing electrically conductive fluid to form a plasmalayer or pocket around the electrode terminal(s), and then inducing thedischarge of energy from this plasma or vapor layer to break themolecular bonds of the tissue structure. Based on initial experiments,applicants believe that the free electrons within the ionized vaporlayer are accelerated in the high electric fields near the electrodetip(s). When the density of the vapor layer (or within a bubble formedin the electrically conducting liquid) becomes sufficiently low (i.e.,less than approximately 10²⁰ atoms/cm³ for aqueous solutions), theelectron mean free path increases to enable subsequently injectedelectrons to cause impact ionization within these regions of low density(i.e., vapor layers or bubbles). Energy evolved by the energeticelectrons (e.g., 4 to 5 eV) can subsequently bombard a molecule andbreak its bonds, dissociating a molecule into free radicals, which thencombine into final gaseous or liquid species.

The energy evolved by the energetic electrons may be varied by adjustinga variety of factors, such as: the number of electrode terminals;electrode size and spacing; electrode surface area; asperities and sharpedges on the electrode surfaces; electrode materials; applied voltageand power; current limiting means, such as inductors; electricalconductivity of the fluid in contact with the electrodes; density of thefluid; and other factors. Accordingly, these factors can be manipulatedto control the energy level of the excited electrons. Since differenttissue structures have different molecular bonds, the present inventioncan be configured to break the molecular bonds of certain tissue, whilehaving too low an energy to break the molecular bonds of other tissue.For example, fatty tissue, (e.g., adipose) tissue has double bonds thatrequire a substantially higher energy level than 4 to 5 eV to break.Accordingly, the present invention in its current configurationgenerally does not ablate or remove such fatty tissue. Of course,factors may be changed such that these double bonds can also be brokenin a similar fashion as the single bonds (e.g., increasing voltage orchanging the electrode configuration to increase the current density atthe electrode tips).

The electrosurgical probe or catheter will comprise a shaft or ahandpiece having a proximal end and a distal end which supports one ormore electrode terminal(s). The shaft or handpiece may assume a widevariety of configurations, with the primary purpose being tomechanically support the active electrode and permit the treatingphysician to manipulate the electrode from a proximal end of the shaft.The shaft may be rigid or flexible, with flexible shafts optionallybeing combined with a generally rigid external tube for mechanicalsupport. Flexible shafts may be combined with pull wires, shape memoryactuators, and other known mechanisms for effecting selective deflectionof the distal end of the shaft to facilitate positioning of theelectrode array. The shaft will usually include a plurality of wires orother conductive elements running axially therethrough to permitconnection of the electrode array to a connector at the proximal end ofthe shaft.

For procedures within the nose, the shaft will have a suitable diameterand length to allow the surgeon to reach the target site (e.g., ablockage in the nasal cavity or one of the sinuses) by delivering theprobe shaft through one of the nasal passages or another opening (e.g.,an opening in the eye or through an opening surgically creating duringthe procedure). Thus, the shaft will usually have a length in the rangeof about 5-25 cm, and a diameter in the range of about 0.5 to 5 mm. Forprocedures requiring the formation of a small hole or channel in tissue,such as treating swollen turbinates, the shaft diameter will usually beless than 3 mm, preferably less than about 1 mm. Likewise, forprocedures in the ear, the shaft should have a length in the range ofabout 3 to 20 cm, and a diameter of about 0.3 to 5 mm. For procedures inthe mouth or upper throat, the shaft will have any suitable length anddiameter that would facilitate handling by the surgeon. For proceduresin the lower throat, such as laryngectomies, the shaft will be suitablydesigned to access the larynx. For example, the shaft may be flexible,or have a distal bend to accommodate the bend in the patient's throat.In this regard, the shaft may be a rigid shaft having a specificallydesigned bend to correspond with the geometry of the mouth and throat,or it may have a flexible distal end, or it may be part of a catheter. Amore complete description of such systems and methods for treatingtissue in the head and neck can be found in U.S. patent applicationentitled “Systems and Methods for Electrosurgical Endoscopic SinusSurgery, filed on Dec. 15, 1997, previously incorporated herein byreference.

For endoscopic procedures within the spine, the shaft will have asuitable diameter and length to allow the surgeon to reach the targetsite (e.g., a disc) by delivering the shaft through the thoracic cavity,the abdomen or the like. Thus, the shaft will usually have a length inthe range of about 5.0 to about 30.0 cm, and a diameter in the range ofabout 0.2 to about 20 mm. Alternatively, the shaft may be delivereddirectly through the patient's back in a posterior approach, which wouldconsiderably reduce the required length of the shaft. In any of theseembodiments, the shaft may also be introduced through rigid or flexibleendoscopes. Specific shaft designs will be described in detail inconnection with the figures hereinafter. A more complete description ofsystems and methods for spine surgery can be found in U.S. patentapplication entitled “Systems and Methods for Electrosurgical SpineSurgery, filed on Feb. 20, 1998, previously incorporated herein byreference.

In an alternative embodiment, the probe may comprise a long, thin needle(e.g., on the order of about 1 mm in diameter or less) that can bepercutaneously introduced through the patient's back directly into thespine. The needle will include one or more active electrode(s) forapplying electrical energy to tissues within the spine. The needle mayinclude one or more return electrode(s), or the return electrode may bepositioned on the patient's back, as a dispersive pad. In eitherembodiment, sufficient electrical energy is applied through the needleto the active electrode(s) to either shrink the collagen fibers withinthe spinal disk, or to ablate tissue within the disk.

The current flow path between the electrode terminal(s) and the returnelectrode(s) may be generated by submerging the tissue site in anelectrical conducting fluid (e.g., within a viscous fluid, such as anelectrically conductive gel) or by directing an electrically conductingfluid along a fluid path to the target site (i.e., a liquid, such asisotonic saline, or a gas, such as argon). This latter method isparticularly effective in a dry environment (i.e., the tissue is notsubmerged in fluid) because the electrically conducting fluid provides asuitable current flow path from the electrode terminal to the returnelectrode. A more complete description of an exemplary method ofdirecting electrically conducting fluid between the active and returnelectrodes is described in parent application Ser. No. 08/485,219, filedJun. 7, 1995 (docket no. 16238-000600), previously incorporated hereinby reference.

In some procedures, it may also be necessary to retrieve or aspirate theelectrically conductive fluid after it has been directed to the targetsite. In addition, it may be desirable to aspirate small pieces oftissue that are not completely disintegrated by the high frequencyenergy, or other fluids at the target site, such as blood, mucus, thegaseous products of ablation, etc. Accordingly, the system of thepresent invention will usually include a suction lumen in the probe, oron another instrument, for aspirating fluids from the target site. Inaddition, the invention may include one or more aspiration electrode(s)coupled to the distal end of the suction lumen for ablating, or at leastreducing the volume of, non-ablated tissue fragments that are aspiratedinto the lumen. The aspiration electrode(s) function mainly to inhibitclogging of the lumen that may otherwise occur as larger tissuefragments are drawn therein. The aspiration electrode(s) may bedifferent from the ablation electrode terminal(s), or the sameelectrode(s) may serve both functions. A more complete description ofprobes incorporating aspiration electrode(s) can be found in conmmonlyassigned, co-pending patent application entitled “Systems And MethodsFor Tissue Resection, Ablation And Aspiration”, filed Jan. 21, 1998, thecomplete disclosure of which is incorporated herein by reference.

The present invention may use a single active electrode terminal or anelectrode array distributed over a contact surface of a probe. In thelatter embodiment, the electrode array usually includes a plurality ofindependently current-limited and/or power-controlled electrodeterminals to apply electrical energy selectively to the target tissuewhile limiting the unwanted application of electrical energy to thesurrounding tissue and environment resulting from power dissipation intosurrounding electrically conductive liquids, such as blood, normalsaline, electrically conductive gel and the like. The electrodeterminals may be independently current-limited by isolating theterminals from each other and connecting each terminal to a separatepower source that is isolated from the other electrode terminals.Alternatively, the electrode terminals may be connected to each other ateither the proximal or distal ends of the probe to form a single wirethat couples to a power source.

The active electrode(s) are typically mounted in an electricallyinsulating electrode support that extends from the electrosurgicalprobe. In some embodiments, the electrode support comprises a pluralityof wafer layers bonded together, e.g., by a glass adhesive or the like,or a single wafer. The wafer layer(s) have conductive strips printedthereon to form the electrode terminal(s) and the return electrode(s).In one embodiment, the proximal end of the wafer layer(s) will have anumber of holes extending from the conductor strips to an exposedsurface of the wafer layers for connection to electrical conductor leadtraces in the electrosurgical probe or handpiece. The wafer layerspreferably comprise a ceramic material , such as alumina, and theelectrode will preferably comprise a metallic material, such as gold,copper, platinum, palladium, tungsten, silver or the like. Suitablemultilayer ceramic electrodes are commercially available from e.g.,VisPro Corporation of Beaverton, Oreg.

In one configuration, each individual electrode terminal in theelectrode array is electrically insulated from all other electrodeterminals in the array within said probe and is connected to a powersource which is isolated from each of the other electrode terminals inthe array or to circuitry which limits or interrupts current flow to theelectrode terminal when low resistivity material (e.g., blood,electrically conductive saline irrigant or electrically conductive gel)causes a lower impedance path between the return electrode and theindividual electrode terminal. The isolated power sources for eachindividual electrode terminal may be separate power supply circuitshaving internal impedance characteristics which limit power to theassociated electrode terminal when a low impedance return path isencountered. By way of example, the isolated power source may be a userselectable constant current source. In this embodiment, lower impedancepaths will automatically result in lower resistive heating levels sincethe heating is proportional to the square of the operating current timesthe impedance. Alternatively, a single power source may be connected toeach of the electrode terminals through independently actuatableswitches, or by independent current limiting elements, such asinductors, capacitors, resistors and/or combinations thereof. Thecurrent limiting elements may be provided in the probe, connectors,cable, controller or along the conductive path from the controller tothe distal tip of the probe. Alternatively, the resistance and/orcapacitance may occur on the surface of the active electrode terminal(s)due to oxide layers which form selected electrode terminals (e.g.,titanium or a resistive coating on the surface of metal, such asplatinum).

The tip region of the probe may comprise many independent electrodeterminals designed to deliver electrical energy in the vicinity of thetip. The selective application of electrical energy to the conductivefluid is achieved by connecting each individual electrode terminal andthe return electrode to a power source having independently controlledor current limited channels. The return electrode(s) may comprise asingle tubular member of conductive material proximal to the electrodearray at the tip which also serves as a conduit for the supply of theelectrically conducting fluid between the active and return electrodes.Alternatively, the probe may comprise an array of return electrodes atthe distal tip of the probe (together with the active electrodes) tomaintain the electric current at the tip. The application of highfrequency voltage between the return electrode(s) and the electrodearray results in the generation of high electric field intensities atthe distal tips of the electrode terminals with conduction of highfrequency current from each individual electrode terminal to the returnelectrode. The current flow from each individual electrode terminal tothe return electrode(s) is controlled by either active or passive means,or a combination thereof, to deliver electrical energy to thesurrounding conductive fluid while minimizing energy delivery tosurrounding (non-target) tissue.

The application of a high frequency voltage between the returnelectrode(s) and the electrode terminal(s) for appropriate timeintervals effects cutting, removing, ablating, shaping, contracting orotherwise modifying the target tissue. The tissue volume over whichenergy is dissipated (i.e., a high current density exists) may beprecisely controlled, for example, by the use of a multiplicity of smallelectrode terminals whose effective diameters or principal dimensionsrange from about 5 mm to 0.01 mm, preferably from about 2 mm to 0.05 mm,and more preferably from about 1 mm to 0.1 mm. Electrode areas for bothcircular and non-circular terminals will have a contact area (perelectrode terminal) below 25 mm², preferably being in the range from0.0001 mm² to 1 mm², and more preferably from 0.005 mm² to 0.5 mm². Thecircumscribed area of the electrode array is in the range from 0.25 mm²to 75 mm², preferably from 0.5 mm² to 40 mm², and will usually includeat least two isolated electrode terminals, preferably at least fiveelectrode terminals, often greater than 10 electrode terminals and even50 or more electrode terminals, disposed over the distal contactsurfaces on the shaft. The use of small diameter electrode terminalsincreases the electric field intensity and reduces the extent or depthof tissue heating as a consequence of the divergence of current fluxlines which emanate from the exposed surface of each electrode terminal.

The area of the tissue treatment surface can vary widely, and the tissuetreatment surface can assume a variety of geometries, with particularareas and geometries being selected for specific applications. Activeelectrode surfaces can have areas in the range from 0.25 mm² to 75 mm²,usually being from about 0.5 mm² to 40 mm². The geometries can beplanar, concave, convex, hemispherical, conical, linear “in-line” arrayor virtually any other regular or irregular shape. Most commonly, theactive electrode(s) or electrode terminal(s) will be formed at thedistal tip of the electrosurgical probe shaft, frequently being planar,disk-shaped, or hemispherical surfaces for use in reshaping proceduresor being linear arrays for use in cutting. Alternatively oradditionally, the active electrode(s) may be formed on lateral surfacesof the electrosurgical probe shaft (e.g., in the manner of a spatula),facilitating access to certain body structures in endoscopic procedures.

In the representative embodiments, the electrode terminals comprisesubstantially rigid wires protruding outward from the tissue treatmentsurface of the electrode support member. Usually, the wires will extendabout 0.1 to 4.0 mm, preferably about 0.2 to 1 mm, from the distalsurface of the support member. In the exemplary embodiments, theelectrosurgical probe includes between about two to fifty electricallyisolated electrode terminals, and preferably between about three totwenty electrode terminals.

The electrically conducting fluid should have a threshold conductivityto provide a suitable conductive path between the return electrode(s)and the electrode terminal(s). The electrical conductivity of the fluid(in units of milliSiemans per centimeter or mS/cm) will usually begreater than 0.2 mS/cm, preferably will be greater than 2 mS/cm and morepreferably greater than 10 mS/cm. In an exemplary embodiment, theelectrically conductive fluid is isotonic saline, which has aconductivity of about 17 mS/cm.

In some embodiments, the electrode support and the fluid outlet may berecessed from an outer surface of the probe or handpiece to confine theelectrically conductive fluid to the region immediately surrounding theelectrode support. In addition, the shaft may be shaped so as to form acavity around the electrode support and the fluid outlet. This helps toassure that the electrically conductive fluid will remain in contactwith the electrode terminal(s) and the return electrode(s) to maintainthe conductive path therebetween. In addition, this will help tomaintain a vapor or plasma layer between the electrode terminal(s) andthe tissue at the treatment site throughout the procedure, which reducesthe thermal damage that might otherwise occur if the vapor layer wereextinguished due to a lack of conductive fluid. Provision of theelectrically conductive fluid around the target site also helps tomaintain the tissue temperature at desired levels.

The voltage applied between the return electrode(s) and the electrodearray will be at high or radio frequency, typically between about 5 kHzand 20 MHz, usually being between about 30 kHz and 2.5 MHz, preferablybeing between about 50 kHz and 500 kHz, more preferably less than 350kHz, and most preferably between about 100 kHz and 200 kHz. The RMS(root mean square) voltage applied will usually be in the range fromabout 5 volts to 1000 volts, preferably being in the range from about 10volts to 500 volts depending on the electrode terminal size, theoperating frequency and the operation mode of the particular procedureor desired effect on the tissue (i.e., contraction, coagulation orablation). Typically, the peak-to-peak voltage will be in the range of10 to 2000 volts, preferably in the range of 20 to 1200 volts and morepreferably in the range of about 40 to 800 volts (again, depending onthe electrode size, the operating frequency and the operation mode).

As discussed above, the voltage is usually delivered in a series ofvoltage pulses or alternating current of time varying voltage amplitudewith a sufficiently high frequency (e.g., on the order of 5 kHz to 20MHz) such that the voltage is effectively applied continuously (ascompared with e.g., lasers claiming small depths of necrosis, which aregenerally pulsed about 10 to 20 Hz). In addition, the duty cycle (i.e.,cumulative time in any one-second interval that energy is applied) is onthe order of about 50% for the present invention, as compared withpulsed lasers which typically have a duty cycle of about 0.0001%.

The preferred power source of the present invention delivers a highfrequency current selectable to generate average power levels rangingfrom several milliwatts to tens of watts per electrode, depending on thevolume of target tissue being heated, and/or the maximum allowedtemperature selected for the probe tip. The power source allows the userto select the voltage level according to the specific requirements of aparticular FESS procedure, arthroscopic surgery, dermatologicalprocedure, ophthalmic procedures, open surgery or other endoscopicsurgery procedure. A description of a suitable power source can be foundin U.S. Provisional Application No. 60/062,997, filed on Oct. 23, 1997entitled “Systems And Methods For Electrosurgical Tissue And FluidCoagulation” (Attorney Docket No. 16238-007400), the complete disclosureof which has been incorporated herein by reference.

The power source may be current limited or otherwise controlled so thatundesired heating of the target tissue or surrounding (non-target)tissue does not occur. In a presently preferred embodiment of thepresent invention, current limiting inductors are placed in series witheach independent electrode terminal, where the inductance of theinductor is in the range of 10 uH to 50,000 uH, depending on theelectrical properties of the target tissue, the desired tissue heatingrate and the operating frequency. Alternatively, capacitor-inductor (LC)circuit structures may be employed, as described previously inco-pending PCT application No. PCT/US94/05168, the complete disclosureof which is incorporated herein by reference. Additionally, currentlimiting resistors may be selected. Preferably, these resistors willhave a large positive temperature coefficient of resistance so that, asthe current level begins to rise for any individual electrode terminalin contact with a low resistance medium (e.g., saline irrigant orconductive gel), the resistance of the current limiting resistorincreases significantly, thereby minimizing the power delivery from saidelectrode terminal into the low resistance medium (e.g., saline irrigantor conductive gel).

It should be clearly understood that the invention is not limited toelectrically isolated electrode terminals, or even to a plurality ofelectrode terminals. For example, the array of active electrodeterminals may be connected to a single lead that extends through theprobe shaft to a power source of high frequency current. Alternatively,the probe may incorporate a single electrode that extends directlythrough the probe shaft or is connected to a single lead that extends tothe power source. The active electrode may have a ball shape (e.g., fortissue vaporization and desiccation), a twizzle shape (for vaporizationand needle-like cutting), a spring shape (for rapid tissue debulking anddesiccation), a twisted metal shape, an annular or solid tube shape orthe like. Alternatively, the electrode may comprise a plurality offilaments, a rigid or flexible brush electrode (for debulking a tumor,such as a fibroid, bladder tumor or a prostate adenoma), a side-effectbrush electrode on a lateral surface of the shaft, a coiled electrode orthe like. In one embodiment, the probe comprises a single activeelectrode terminal that extends from an insulating member, e.g.,ceramic, at the distal end of the probe. The insulating member ispreferably a tubular structure that separates the active electrodeterminal from a tubular or annular return electrode positioned proximalto the insulating member and the active electrode.

Referring to FIG. 2, an exemplary electrosurgical system 11 fortreatment of tissue or other body structures will now be described indetail. Electrosurgical system 11 generally comprises an electrosurgicalhandpiece or probe 10 connected to a power supply 28 for providing highfrequency voltage to a target site and a fluid source 21 for supplyingelectrically conducting fluid 50 to probe 10. In addition,electrosurgical system 11 may include an endoscope (not shown) with afiber optic head light for viewing the surgical site, particularly inspinal or sinus procedures or procedures in the ear or the back of themouth. The endoscope may be integral with probe 10, or it may be part ofa separate instrument. The system 11 may also include a vacuum source(not shown) for coupling to a suction lumen or tube 205 (see FIG. 3) inthe probe 10 for aspirating the target site.

As shown, probe generally includes a proximal handle 19 and an elongateshaft 18 having an array 12 of electrode terminals 58 at its distal end.A connecting cable 34 has a connector 26 for electrically coupling theelectrode terminals 58 to power supply 28. The electrode terminals 58are electrically isolated from each other and each of the terminals 58is connected to an active or passive control network within power supply28 by means of a plurality of individually insulated conductors (notshown). A fluid supply tube 15 is connected to a fluid tube 14 of probe10 for supplying electrically conducting fluid 50 to the target site.

Power supply 28 has an operator controllable voltage level adjustment 30to change the applied voltage level, which is observable at a voltagelevel display 32. Power supply 28 also includes first, second and thirdfoot pedals 37, 38, 39 and a cable 36 which is removably coupled topower supply 28. The foot pedals 37, 38, 39 allow the surgeon toremotely adjust the energy level applied to electrode terminals 58. Inan exemplary embodiment, first foot pedal 37 is used to place the powersupply into the “ablation” mode and second foot pedal 38 places powersupply 28 into the “coagulation” mode. The third foot pedal 39 allowsthe user to adjust the voltage level within the “ablation” mode. In theablation mode, a sufficient voltage is applied to the electrodeterminals to establish the requisite conditions for moleculardissociation of the tissue (i.e., vaporizing a portion of theelectrically conductive fluid, ionizing charged particles within thevapor layer and accelerating these charged particles against thetissue). As discussed above, the requisite voltage level for ablationwill vary depending on the number, size, shape and spacing of theelectrodes, the distance in which the electrodes extend from the supportmember, etc. Once the surgeon places the power supply in the “ablation”mode, voltage level adjustment 30 or third foot pedal 39 may be used toadjust the voltage level to adjust the degree or aggressiveness of theablation. A more complete description of an exemplary power supply foruse with the present invention can be found in co-pending ProvisionalPatent Application entitled “Systems And Methods For ElectrosurgicalTissue And Fluid Coagulation”, filed Feb. 18, 1998, the completedisclosure of which is incorporated herein by reference for allpurposes.

Of course, it will be recognized that the voltage and modality of thepower supply may be controlled by other input devices. However,applicant has found that foot pedals are convenient methods ofcontrolling the power supply while manipulating the probe during asurgical procedure.

In the coagulation mode, the power supply 28 applies a low enoughvoltage to the electrode terminals (or the coagulation electrode) toavoid vaporization of the electrically conductive fluid and subsequentmolecular dissociation of the tissue. The surgeon may automaticallytoggle the power supply between the ablation and coagulation modes byalternatively stepping on foot pedals 37, 38, respectively. This allowsthe surgeon to quickly move between coagulation and ablation in situ,without having to remove his/her concentration from the surgical fieldor without having to request an assistant to switch the power supply. Byway of example, as the surgeon is sculpting soft tissue in the ablationmode, the probe typically will simultaneously seal and/or coagulationsmall severed vessels within the tissue. However, larger vessels, orvessels with high fluid pressures (e.g., arterial vessels) may not besealed in the ablation mode. Accordingly, the surgeon can simply step onfoot pedal 38, automatically lowering the voltage level below thethreshold level for ablation, and apply sufficient pressure onto thesevered vessel for a sufficient period of time to seal and/or coagulatethe vessel. After this is completed, the surgeon may quickly move backinto the ablation mode by stepping on foot pedal 37. A specific designof a suitable power supply for use with the present invention can befound in U.S. Provisional Patent Application No. 60/062,997, filed Oct.23, 1997, entitled “Systems And Methods For Electrosurgical Tissue AndFluid Coagulation” (Attorney Docket No. 16238-007400), previouslyincorporated herein by reference.

FIGS. 3-5 illustrate an exemplary electrosurgical probe 20 constructedaccording to the principles of the present invention. As shown in FIG.2, probe 20 generally includes an elongated shaft 100 which may beflexible or rigid, a handle 204 coupled to the proximal end of shaft 100and an electrode support member 102 coupled to the distal end of shaft100. Shaft 100 preferably comprises a plastic material that is easilymolded into the shape shown in FIG. 3. In an alternative embodiment (notshown), shaft 100 comprises an electrically conducting material, usuallymetal, which is selected from the group comprising tungsten, stainlesssteel alloys, platinum or its alloys, titanium or its alloys, molybdenumor its alloys, and nickel or its alloys. In this embodiment, shaft 100includes an electrically insulating jacket 108, which is typicallyformed as one or more electrically insulating sheaths or coatings, suchas polytetrafluoroethylene, polyimide, and the like. The provision ofthe electrically insulating jacket over the shaft prevents directelectrical contact between these metal elements and any adjacent bodystructure or the surgeon. Such direct electrical contact between a bodystructure (e.g., tendon) and an exposed electrode could result inunwanted heating and necrosis of the structure at the point of contactcausing necrosis.

Handle 204 typically comprises a plastic material that is easily moldedinto a suitable shape for handling by the surgeon. Handle 204 defines aninner cavity (not shown) that houses the electrical connections 250(FIG. 5), and provides a suitable interface for connection to anelectrical connecting cable 22 (see FIG. 2). Electrode support member102 extends from the distal end of shaft 100 (usually about 1 to 20 mm),and provides support for a plurality of electrically isolated electrodeterminals 104 (see FIG. 4B). As shown in FIG. 3, a fluid tube 233extends through an opening in handle 204, and includes a connector 235for connection to a fluid supply source, for supplying electricallyconductive fluid to the target site. Fluid tube 233 is coupled to adistal fluid tube 239 that extends along the outer surface of shaft 100to an opening 237 at the distal end of the probe 20, as discussed indetail below. Of course, the invention is not limited to thisconfiguration. For example, fluid tube 233 may extend through a singlelumen (not shown) in shaft 100, or it may be coupled to a plurality oflumens (also not shown) that extend through shaft 100 to a plurality ofopenings at its distal end. Probe 20 may also include a valve 17 (FIG.2) or equivalent structure for controlling the flow rate of theelectrically conducting fluid to the target site.

As shown in FIGS. 4A and 4B, electrode support member 102 has asubstantially planar tissue treatment surface 212 and comprises asuitable insulating material (e.g., ceramic or glass material, such asalumina, zirconia and the like) which could be formed at the time ofmanufacture in a flat, hemispherical or other shape according to therequirements of a particular procedure. The preferred support membermaterial is alumina, available from Kyocera Industrial CeramicsCorporation, Elkgrove, Ill., because of its high thermal conductivity,good electrically insulative properties, high flexural modulus,resistance to carbon tracking, biocompatibility, and high melting point.The support member 102 is adhesively joined to a tubular support member(not shown) that extends most or all of the distance between supportmember 102 and the proximal end of probe 20. The tubular memberpreferably comprises an electrically insulating material, such as anepoxy or silicone-based material.

In a preferred construction technique, electrode terminals 104 extendthrough pre-formed openings in the support member 102 so that theyprotrude above tissue treatment surface 212 by the desired distance. Theelectrodes are then bonded to the tissue treatment surface 212 ofsupport member 102, typically by an inorganic sealing material. Thesealing material is selected to provide effective electrical insulation,and good adhesion to both the alumina member 102 and the platinum ortitanium electrode terminals 104. The sealing material additionallyshould have a compatible thermal expansion coefficient and a meltingpoint well below that of platinum or titanium and alumina or zirconia,typically being a glass or glass ceramic

In the embodiment shown in FIGS. 3-5, probe 20 includes a returnelectrode 112 for completing the current path between electrodeterminals 104 and a high frequency power supply 28 (see FIG. 2). Asshown, return electrode 112 preferably comprises an annular conductiveband coupled to the distal end of shaft 100 slightly proximal to tissuetreatment surface 212 of electrode support member 102, typically about0.5 to 10 mm and more preferably about 1 to 10 mm. Return electrode 112is coupled to a connector 258 that extends to the proximal end of probe10, where it is suitably connected to power supply 10 (FIG. 2).

As shown in FIG. 3, return electrode 112 is not directly connected toelectrode terminals 104. To complete this current path so that electrodeterminals 104 are electrically connected to return electrode 112,electrically conducting fluid (e.g., isotonic saline) is caused to flowtherebetween. In the representative embodiment, the electricallyconducting fluid is delivered through an external fluid tube 239 toopening 237, as described above. Alternatively, the fluid may bedelivered by a fluid delivery element (not shown) that is separate fromprobe 20. In some microendoscopic discectomy procedures, for example,the trocar cannula may be flooded with isotonic saline and the probe 20will be introduced into this flooded cavity. Electrically conductingfluid will be continually resupplied with a separate instrument tomaintain the conduction path between return electrode 112 and electrodeterminals 104.

In alternative embodiments, the fluid path may be formed in probe 20 by,for example, an inner lumen or an annular gap between the returnelectrode and a tubular support member within shaft 100 (not shown).This annular gap may be formed near the perimeter of the shaft 100 suchthat the electrically conducting fluid tends to flow radially inwardtowards the target site, or it may be formed towards the center of shaft100 so that the fluid flows radially outward. In both of theseembodiments, a fluid source (e.g., a bag of fluid elevated above thesurgical site or having a pumping device), is coupled to probe 90 via afluid supply tube (not shown) that may or may not have a controllablevalve. A more complete description of an electrosurgical probeincorporating one or more fluid lumen(s) can be found in parentapplication U.S. Pat. No. 5,697,281, filed on Jun. 7, 1995 (AttorneyDocket 16238-0006000), the complete disclosure of which has previouslybeen incorporated herein by reference.

Referring to FIG. 4B, the electrically isolated electrode terminals 104are spaced apart over tissue treatment surface 212 of electrode supportmember 102. The tissue treatment surface and individual electrodeterminals 104 will usually have dimensions within the ranges set forthabove. In the representative embodiment, the tissue treatment surface212 has a circular cross-sectional shape with a diameter in the range ofabout 1 mm to 30 mm, usually about 2 to 20 mm. The individual electrodeterminals 104 preferably extend outward from tissue treatment surface212 by a distance of about 0.1 to 8 mm, usually about 0.2 to 4 mm.Applicant has found that this configuration increases the high electricfield intensities and associated current densities around electrodeterminals 104 to facilitate the ablation of tissue as described indetail above.

In the embodiment of FIGS. 3-5, the probe includes a single, largeropening 209 in the center of tissue treatment surface 212, and aplurality of electrode terminals (e.g., about 3-15) around the perimeterof surface 212 (see FIG. 4A). Alternatively, the probe may include asingle, annular, or partially annular, electrode terminal at theperimeter of the tissue treatment surface. The central opening 209 iscoupled to a suction or aspiration lumen 213 (see FIG. 3) within shaft100 and a suction tube 211 (FIG. 3) for aspirating tissue, fluids and/orgases from the target site. In this embodiment, the electricallyconductive fluid generally flows from opening 237 of fluid tube 239radially inward past electrode terminals 104 and then back through thecentral opening 209 of support member 102. Aspirating the electricallyconductive fluid during surgery allows the surgeon to see the targetsite, and it prevents the fluid from flowing into the patient's body,e.g., into the spine, the abdomen or the thoracic cavity. Thisaspiration should be controlled, however, so that the conductive fluidmaintains a conductive path between the active electrode terminal(s) andthe return electrode.

Of course, it will be recognized that the distal tip of probe may have avariety of different configurations. For example, the probe may includea plurality of openings 209 around the outer perimeter of tissuetreatment surface 212 (this embodiment not shown in the drawings). Inthis embodiment, the electrode terminals 104 extend from the center oftissue treatment surface 212 radially inward from openings 209. Theopenings are suitably coupled to fluid tube 233 for deliveringelectrically conductive fluid to the target site, and aspiration lumen213 for aspirating the fluid after it has completed the conductive pathbetween the return electrode 112 and the electrode terminals 104.

In some embodiments, the probe 20 will also include one or moreaspiration electrode(s) coupled to the aspiration lumen for inhibitingclogging during aspiration of tissue fragments from the surgical site.As shown in FIG. 6, one or more of the active electrode terminals 104may comprise loop electrodes 140 that extend across distal opening 209of the suction lumen within shaft 100. In the representative embodiment,two of the electrode terminals 104 comprise loop electrodes 140 thatcross over the distal opening 209. Of course, it will be recognized thata variety of different configurations are possible, such as a singleloop electrode, or multiple loop electrodes having differentconfigurations than shown. In addition, the electrodes may have shapesother than loops, such as the coiled configurations shown in FIGS. 6 and7. Alternatively, the electrodes may be formed within suction lumenproximal to the distal opening 209, as shown in FIG. 8. The mainfunction of loop electrodes 140 is to ablate portions of tissue that aredrawn into the suction lumen to prevent clogging of the lumen.

Loop electrodes 140 are electrically isolated from the other electrodeterminals 104, which can be referred to hereinafter as the ablationelectrodes 104. Loop electrodes 140 may or may not be electricallyisolated from each other. Loop electrodes 140 will usually extend onlyabout 0.05 to 4 mm, preferably about 0.1 to 1 mm from the tissuetreatment surface of electrode support member 104.

Referring now to FIGS. 7 and 8, alternative embodiments for aspirationelectrodes will now be described. As shown in FIG. 7, the aspirationelectrodes may comprise a pair of coiled electrodes 150 that extendacross distal opening 209 of the suction lumen. The larger surface areaof the coiled electrodes 150 usually increases the effectiveness of theelectrodes 150 on tissue fragments passing through opening 209. In FIG.8, the aspiration electrode comprises a single coiled electrode 152passing across the distal opening 209 of suction lumen. This singleelectrode 152 may be sufficient to inhibit clogging of the suctionlumen. Alternatively, the aspiration electrodes may be positioned withinthe suction lumen proximal to the distal opening 209. Preferably, theseelectrodes are close to opening 209 so that tissue does not clog theopening 209 before it reaches electrodes 154. In this embodiment, aseparate return electrode 156 may be provided within the suction lumento confine the electric currents therein.

Referring to FIG. 10, another embodiment of the present inventionincorporates an aspiration electrode 160 within the aspiration lumen 162of the probe. As shown, the electrode 160 is positioned just proximal ofdistal opening 209 so that the tissue fragments are ablated as theyenter lumen 162. In the representation embodiment, the aspirationelectrode 160 comprises a loop electrode that stretches across theaspiration lumen 162. However, it will be recognized that many otherconfigurations are possible. In this embodiment, the return electrode164 is located outside of the probe as in the previously embodiments.Alternatively, the return electrode(s) may be located within theaspiration lumen 162 with the aspiration electrode 160. For example, theinner insulating coating 163 may be exposed at portions within the lumen162 to provide a conductive path between this exposed portion of returnelectrode 164 and the aspiration electrode 160. The latter embodimenthas the advantage of confining the electric currents to within theaspiration lumen. In addition, in dry fields in which the conductivefluid is delivered to the target site, it is usually easier to maintaina conductive fluid path between the active and return electrodes in thelatter embodiment because the conductive fluid is aspirated through theaspiration lumen 162 along with the tissue fragments.

Referring to FIG. 9, another embodiment of the present inventionincorporates a wire mesh electrode 600 extending across the distalportion of aspiration lumen 162. As shown, mesh electrode 600 includes aplurality of openings 602 to allow fluids and tissue fragments to flowthrough into aspiration lumen 162. The size of the openings 602 willvary depending on a variety of factors. The mesh electrode may becoupled to the distal or proximal surfaces of ceramic support member102. Wire mesh electrode 600 comprises a conductive material, such astitanium, tantalum, steel, stainless steel, tungsten, copper, gold orthe like. In the representative embodiment, wire mesh electrode 600comprises a different material having a different electric potentialthan the active electrode terminal(s) 104. Preferably, mesh electrode600 comprises steel and electrode terminal(s) comprises tungsten.Applicant has found that a slight variance in the electrochemicalpotential of mesh electrode 600 and electrode terminal(s) 104 improvesthe performance of the device. Of course, it will be recognized that themesh electrode may be electrically insulated from active electrodeterminal(s) as in previous embodiments

Referring now to FIGS. 11A-11C, an alternative embodiment incorporatinga metal screen 610 is illustrated. As shown, metal screen 610 has aplurality of peripheral openings 612 for receiving electrode terminals104, and a plurality of inner openings 614 for allowing aspiration offluid and tissue through opening 609 of the aspiration lumen. As shown,screen 610 is press fitted over electrode terminals 104 and then adheredto shaft 100 of probe 20. Similar to the mesh electrode embodiment,metal screen 610 may comprise a variety of conductive metals, such astitanium, tantalum, steel, stainless steel, tungsten, copper, gold orthe like. In the representative embodiment, metal screen 610 is coupleddirectly to, or integral with, active electrode terminal(s) 104. In thisembodiment, the active electrode terminal(s) 104 and the metal screen610 are electrically coupled to each other.

In other embodiments (now shown), the aspiration lumen may be formed onthe perimeter of the shaft 100 (e.g., an annular or semi-annular lumen)rather than in the center, as described above. In these embodiments, theaspiration lumen is preferably set back proximally from the electrodeterminals 104 by a distance of about 0.2 mm to 10 cm, preferably about0.5 mm to 1 cm. In these embodiments, the aspiration lumen may alsoinclude one or more aspiration electrode(s) for reducing clogging asdescribed above. One of the advantages of this configuration is that thesuction of conductive fluid into the aspiration lumen does not interferewith the plasma layer formed at the tips of the electrode terminal(s).This allows the surgeon to provide a relatively large suction force,while still maintaining the requisite conditions for formation of thevapor layer and subsequent molecular dissociation of tissue.

FIG. 5 illustrates the electrical connections 250 within handle 204 forcoupling electrode terminals 104 and return electrode 112 to the powersupply 28. As shown, a plurality of wires 252 extend through shaft 100to couple terminals 104 to a plurality of pins 254, which are pluggedinto a connector block 256 for coupling to a connecting cable 22 (FIG.1). Similarly, return electrode 112 is coupled to connector block 256via a wire 258 and a plug 260.

In some embodiments of the present invention, the probe 20 furtherincludes an identification element that is characteristic of theparticular electrode assembly so that the same power supply 28 can beused for different electrosurgical operations. In one embodiment, forexample, the probe 20 includes a voltage reduction element or a voltagereduction circuit for reducing the voltage applied between the electrodeterminals 104 and the return electrode 112. The voltage reductionelement serves to reduce the voltage applied by the power supply so thatthe voltage between the electrode terminals and the return electrode islow enough to avoid excessive power dissipation into the electricallyconducting medium and/or ablation of the soft tissue at the target site.The voltage reduction element primarily allows the electrosurgical probe20 to be compatible with other ArthroCare generators that are adapted toapply higher voltages for ablation or vaporization of tissue. Forcontraction of tissue, for example, the voltage reduction element willserve to reduce a voltage of about 100 to 135 volts rms (which is asetting of 1 on the ArthroCare Model 970 and 980 (i.e., 2000)Generators) to about 45 to 60 volts rms, which is a suitable voltage forcontraction of tissue without ablation (e.g., molecular dissociation) ofthe tissue.

Of course, for some procedures, the probe will typically not require avoltage reduction element. Alternatively, the probe may include avoltage increasing element or circuit, if desired.

In the representative embodiment, the voltage reduction element is adropping capacitor 262 which has first leg 264 coupled to the returnelectrode wire 258 and a second leg 266 coupled to connector block 256.Of course, the capacitor may be located in other places within thesystem, such as in, or distributed along the length of, the cable, thegenerator, the connector, etc. In addition, it will be recognized thatother voltage reduction elements, such as diodes, transistors,inductors, resistors, capacitors or combinations thereof, may be used inconjunction with the present invention. For example, the probe 90 mayinclude a coded resistor (not shown) that is constructed to lower thevoltage applied between return electrode 112 and electrode terminals 104to a suitable level for contraction of tissue. In addition, electricalcircuits may be employed for this purpose.

Alternatively or additionally, the cable 22 that couples the powersupply 10 to the probe 90 may be used as a voltage reduction element.The cable has an inherent capacitance that can be used to reduce thepower supply voltage if the cable is placed into the electrical circuitbetween the power supply, the electrode terminals and the returnelectrode. In this embodiment, the cable 22 may be used alone, or incombination with one of the voltage reduction elements discussed above,e.g., a capacitor.

In some embodiments, the probe 20 will further include a switch (notshown) or other input that allows the surgeon to couple and decouple theidentification element to the rest of the electronics in the probe 20.For example, if the surgeon would like to use the same probe forablation of tissue and contraction of tissue in the same procedure, thiscan be accomplished by manipulating the switch. Thus, for ablation oftissue, the surgeon will decouple the voltage reduction element from theelectronics so that the full voltage applied by the power source isapplied to the electrodes on the probe. When the surgeon desires toreduce the voltage to a suitable level for contraction of tissue, he/shecouples the voltage reduction element to the electronics to reduce thevoltage applied by the power supply to the electrode terminals.

Further, it should be noted that the present invention can be used witha power supply that is adapted to apply a voltage within the selectedrange for treatment of tissue. In this embodiment, a voltage reductionelement or circuitry may not be desired.

The power supply may also includes one or more current sensors (notshown) for detecting the output current. The sensor is designed for usewith coding resistors in electrosurgical probes to limit the amount ofvoltage applied to the probe according to its design limits. The designlimits are revealed by the internal coding resistor, which is typicallycontained in the handle portion of the disposable probe. This featureallows the power supply to be used with a wide variety of probes and ina wide variety of surgical procedures. In addition, this sensingcapability can be used to detect whether electrically conductive fluidis present adjacent the electrode terminals to prevent energizing theprobe if the appropriate amount of fluid is not present. The generatormay also include a voltage threshold detector for setting peak RF outputvoltage limits.

Referring to FIG. 20, the power output signal is coupled to a pluralityof current limiting elements 96, which are preferably located on adaughter board since the current limiting elements may vary depending onthe application. FIG. 20 illustrates an arrangement that may be used inarthroscopic procedures with a multi-electrode probe. As shown, a highfrequency power supply 28 comprises a voltage source 98 which isconnected to a multiplicity of current limiting elements 96 a, 96 b, . .. 96 z, typically being inductors having an inductance in the range ofabout 100 to 5000 microhenries, with the particular value depending onthe electrode terminal dimensions, the desired ablation rates, and thelike. Capacitors having capacitance values in the range of about 200 to10,000 picofarads may also be used as the current limiting elements. Itwould also be possible to use resistors as current limiting elements.The current limiting elements any also be part of a resonant circuitstructure, as described in detail in PCT/US94/05168.

FIGS. 12-14 illustrate a method for treating nasal or sinus blockages,e.g., chronic sinusitis, according to the present invention. In theseprocedures, the polyps, turbinates or other sinus tissue may be ablatedor reduced (e.g., by tissue contraction) to clear the blockage and/orenlarge the sinus cavity to reestablish normal sinus function. Forexample, in chronic rhinitis, which is a collective term for chronicirritation or inflammation of the nasal mucosa with hypertrophy of thenasal mucosa, the inferior turbinate may be reduced by ablation orcontraction. Alternatively, a turbinectomy or mucotomy may be performedby removing a strip of tissue from the lower edge of the inferiorturbinate to reduce the volume of the turbinate. For treating nasalpolypi, which comprises benign pedicled or sessile masses of nasal orsinus mucosa caused by inflammation, the nasal polypi may be contractedor shrunk, or ablated by the method of the present invention. Fortreating severe sinusitis, a frontal sinus operation may be performed tointroduce the electrosurgical probe to the site of blockage. The presentinvention may also be used to treat diseases of the septum, e.g.,ablating or resecting portions of the septum for removal, straighteningor reimplantation of the septum.

The present invention is particularly useful in functional endoscopicsinus surgery (FESS) in the treatment of sinus disease. In contrast toprior art microdebriders, the electrosurgical probe of the presentinvention effects hemostasis of severed blood vessels, and allows thesurgeon to precisely remove tissue with minimal or no damage tosurrounding tissue, bone, cartilage or nerves. By way of example and notlimitation, the present invention may be used for the followingprocedures: (1) uncinectomy or medial displacement or removal ofportions of the middle turbinate; (2) maxillary, sphenoid or ethmoidsinusotomies or enlargement of the natural ostium of the maxillary,sphenoid, or ethmoid sinuses, respectively; (3) frontal recessdissections, in which polypoid or granulation tissue are removed; (4)polypectomies, wherein polypoid tissue is removed in the case of severenasal polyposis; (5) concha bullosa resections or the thinning ofpolypoid middle turbinate; (6) septoplasty; and the like.

FIGS. 12-14 schematically illustrate an endoscopic sinus surgery (FESS)procedure according to the present invention. As shown in FIG. 12, anendoscope 300 is first introduced through one of the nasal passages 301to allow the surgeon to view the target site, e.g., the sinus cavities.As shown, the endoscope 300 will usually comprise a thin metal tube 302with a lens (not shown) at the distal end 304, and an eyepiece 306 atthe proximal end 308. As shown in FIG. 3, the probe shaft 100 (not shownin FIG. 12) has a bend 101 to facilitate use of both the endoscope andthe probe 90 in the same nasal passage (i.e., the handles of the twoinstruments do not interfere with each other in this embodiment).Alternatively, the endoscope may be introduced transorally through theinferior soft palate to view the nasopharynx. Suitable nasal endoscopesfor use with the present invention are described in U.S. Pat. Nos.4,517,962, 4,844,052, 4,881,523 and 5,167,220, the complete disclosuresof which are incorporated herein by reference for all purposes.

Alternatively, the endoscope 300 may include a sheath (not shown) havingan inner lumen for receiving the electrosurgical probe shaft 100. Inthis embodiment, the shaft 100 will extend through the inner lumen to adistal opening in the endoscope. The shaft will include suitableproximal controls for manipulation of its distal end during the surgicalprocedure.

As shown in FIG. 13, the distal end of probe 90 is introduced throughnasal passage 301 into the nasal cavity 303 (endoscope 300 is not shownin FIG. 12). Depending on the location of the blockage, the electrodeterminals 104 will be positioned adjacent the blockage in the nasalcavity 303, or in one of the paranasal sinuses 305, 307. Note that onlythe frontal sinus 305 and the sphenoidal sinus 307 are shown in FIG. 13,but the procedure is also applicable to the ethmoidal and maxillarysinuses. Once the surgeon has reached the point of major blockage,electrically conductive fluid is delivered through tube 233 and opening237 to the tissue (see FIG. 3). The fluid flows past the returnelectrode 112 to the electrode terminals 104 at the distal end of theshaft. The rate of fluid flow is controlled with valve 17 (FIG. 2) suchthat the zone between the tissue and electrode support 102 is constantlyimmersed in the fluid. The power supply 28 is then turned on andadjusted such that a high frequency voltage difference is appliedbetween electrode terminals 104 and return electrode 112. Theelectrically conductive fluid provides the conduction path (see currentflux lines) between electrode terminals 104 and the return electrode112.

FIG. 13 schematically illustrates the relative position of some of themajor nerves within the nasal cavity. As shown, the fila of theolfactory nerve 309 extend downward into the nasal cavity 303, and thenasopalatine nerve 311 extends across the cavity toward the septum ofthe nose. The optic nerve (not shown) extends from the brain into theretina, and thus extends close to the outer boundary of the nasalcavity. In addition, other cranial nerves (not shown), such as thenasociliary nerve and the posterior superior nasal branches extendthrough the nasal cavity. These nerves can be difficult to visualizewith conventional techniques and instruments. In addition, these nervesoften extend through or around the target tissue. Accordingly, thepresent invention provides the distinct advantage of ablation orotherwise modifying tissue within the nasal cavity without significantlydamaging or impairing the function of these cranial nerves.

FIGS. 14A and 14B illustrate the removal of sinus tissue in more detailAs shown, the high frequency voltage is sufficient to convert theelectrically conductive fluid (not shown) between the target tissue 302and electrode terminal(s)104 into an ionized vapor layer 312 or plasma.As a result of the applied voltage difference between electrodeterminal(s) 104 and the target tissue 302 (i.e., the voltage gradientacross the plasma layer 2312), charged particles 315 in the plasma(viz., electrons) are accelerated towards the tissue. At sufficientlyhigh voltage differences, these charged particles 315 gain sufficientenergy to cause dissociation of the molecular bonds within tissuestructures. This molecular dissociation is accompanied by the volumetricremoval (i.e, ablative sublimation) of tissue and the production of lowmolecular weight gases 314, such as oxygen, nitrogen, carbon dioxide,hydrogen and methane. The short range of the accelerated chargedparticles 315 within the tissue confines the molecular dissociationprocess to the surface layer to minimize damage and necrosis to theunderlying tissue 320.

During the process, the gases 314 will be aspirated through opening 209and suction tube 211 to a vacuum source. In addition, excesselectrically conductive fluid, and other fluids (e.g., blood) will beaspirated from the target site 300 to facilitate the surgeon's view.During ablation of the tissue, the residual heat generated by thecurrent flux lines (typically less than 150° C.), will usually besufficient to coagulate any severed blood vessels at the site. If not,the surgeon may switch the power supply 28 into the coagulation mode bylowering the voltage to a level below the threshold for fluidvaporization, as discussed above. This simultaneous hemostasis resultsin less bleeding and facilitates the surgeon's ability to perform theprocedure. Once the blockage has been removed, aeration and drainage arereestablished to allow the sinuses to heal and return to their normalfunction.

Another advantage of the present invention is the ability to preciselyablate layers of sinus tissue without causing necrosis or thermal damageto the underlying and surrounding tissues or bone. In addition, thevoltage can be controlled so that the energy directed to the target siteis insufficient to ablate bone. In this manner, the surgeon canliterally clean the tissue off the bone, without ablating or otherwiseeffecting significant damage to the bone.

Methods for treating air passage disorders according to the presentinvention will now be described. In these embodiments, anelectrosurgical probe such as one described above can be used to ablatetargeted masses including, but not limited to, the tongue, tonsils,turbinates, soft palate tissues (e.g., the uvula), hard tissue andmucosal tissue. In one embodiment, selected portions of the tongue 314are removed to treat sleep apnea. In this method, the distal end of anelectrosurgical probe 90 is introduced into the patient's mouth 310, asshown in FIG. 15. An endoscope (not shown), or other type of viewingdevice, may also be introduced, or partially introduced, into the mouth310 to allow the surgeon to view the procedure (the viewing device maybe integral with, or separate from, the electrosurgical probe). Theelectrode terminals 104 are positioned adjacent to or against the backsurface 316 of the tongue 314, and electrically conductive fluid isdelivered to the target site, as described above. The power supply 28 isthen activated to remove selected portions of the back of the tongue314, as described above, without damaging sensitive structures, such asnerves, and the bottom portion of the tongue 314.

In another embodiment, the electrosurgical probe of the presentinvention can be used to ablate and/or contract soft palate tissue totreat snoring disorders. In particular, the probe is used to ablate orshrink sections of the uvula 320 without causing unwanted tissue damageunder and around the selected sections of tissue. For tissuecontraction, a sufficient voltage difference is applied between theelectrode terminals 104 and the return electrode 112 to elevate theuvula tissue temperature from normal body temperatures (e.g., 37° C.) totemperatures in the range of 45° C. to 90° C., preferably in the rangefrom 60° C. to 70° C. This temperature elevation causes contraction ofthe collagen connective fibers within the uvula tissue.

FIG. 15 illustrates the hypoglossal nerve 351, which originates in themedulla oblongata, collects into the hypoglossal canal and extends intothe tongue 314, where it functions as the motor nerve of the tongue 314.In procedures that require removal or contraction of tissue within thetongue 314, the present invention has a distinct advantage of being ableto perform these procedures without causing significant damage to thehypoglossal nerve 351.

In one method of tissue contraction according to the present invention,an electrically conductive fluid is delivered to the target site asdescribed above, and heated to a sufficient temperature to inducecontraction or shrinkage of the collagen fibers in the target tissue.The electrically conducting fluid is heated to a temperature sufficientto substantially irreversibly contract the collagen fibers, whichgenerally requires a tissue temperature in the range of about 45° C. to90° C., usually about 60° C. to 70° C. The fluid is heated by applyinghigh frequency electrical energy to the electrode terminal(s) in contactwith the electrically conducting fluid. The current emanating from theelectrode terminal(s) 104 heats the fluid and generates a jet or plumeof heated fluid, which is directed towards the target tissue. The heatedfluid elevates the temperature of the collagen sufficiently to causehydrothermal shrinkage of the collagen fibers. The return electrode 112draws the electric current away from the tissue site to limit the depthof penetration of the current into the tissue, thereby inhibitingmolecular dissociation and breakdown of the collagen tissue andminimizing or completely avoiding damage to surrounding and underlyingtissue structures beyond the target tissue site. In an exemplaryembodiment, the electrode terminal(s) 104 are held away from the tissuea sufficient distance such that the RF current does not pass into thetissue at all, but rather passes through the electrically conductingfluid back to the return electrode. In this embodiment, the primarymechanism for imparting energy to the tissue is the heated fluid, ratherthan the electric current.

In an alternative embodiment, the electrode terminal(s) 104 are broughtinto contact with, or close proximity to, the target tissue so that theelectric current passes directly into the tissue to a selected depth. Inthis embodiment, the return electrode draws the electric current awayfrom the tissue site to limit its depth of penetration into the tissue.Applicant has discovered that the depth of current penetration also canbe varied with the electrosurgical system of the present invention bychanging the frequency of the voltage applied to the electrode terminaland the return electrode. This is because the electrical impedance oftissue is known to decrease with increasing frequency due to theelectrical properties of cell membranes which surround electricallyconductive cellular fluid. At lower frequencies (e.g., less than 350kHz), the higher tissue impedance, the presence of the return electrodeand the electrode terminal configuration of the present invention(discussed in detail below) cause the current flux lines to penetrateless deeply resulting in a smaller depth of tissue heating. In anexemplary embodiment, an operating frequency of about 100 to 200 kHz isapplied to the electrode terminal(s) to obtain shallow depths ofcollagen shrinkage (e.g., usually less than 1.5 mm and preferably lessthan 0.5 mm).

In another aspect of the invention, the size (e.g., diameter orprincipal dimension) of the electrode terminals employed for treatingthe tissue are selected according to the intended depth of tissuetreatment. As described previously in copending patent application PCTInternational Application, U.S. National Phase Serial No.

PCT/US94/05168, the depth of current penetration into tissue increaseswith increasing dimensions of an individual active electrode (assumingother factors remain constant, such as the frequency of the electriccurrent, the return electrode configuration, etc.). The depth of currentpenetration (which refers to the depth at which the current density issufficient to effect a change in the tissue, such as collagen shrinkage,irreversible necrosis, etc.) is on the order of the active electrodediameter for the bipolar configuration of the present invention andoperating at a frequency of about 100 kHz to about 200 kHz. Accordingly,for applications requiring a smaller depth of current penetration, oneor more electrode terminals of smaller dimensions would be selected.Conversely, for applications requiring a greater depth of currentpenetration, one or more electrode terminals of larger dimensions wouldbe selected.

In addition to the above procedures, the system and method of thepresent invention may be used for treating a variety of disorders in themouth 310, pharynx 330, larynx 335, hypopharynx, trachea 340, esophagus350 and the neck 360. For example, tonsillar hyperplasis or other tonsildisorders may be treated with a tonsillectomy by partially ablating thelymphoepithelial tissue. This procedure is usually carried out underintubation anesthesia with the head extended. An incision is made in theanterior faucial pillar, and the connective tissue layer between thetonsillar parenchyma and the pharyngeal constrictor muscles isdemonstrated. The incision may be made with conventional scalpels, orwith the electrosurgical probe of the present invention. The tonsil isthen freed by ablating through the upper pole to the base of the tongue,preserving the faucial pillars. The probe ablates the tissue, whileproviding simultaneous hemostasis of severed blood vessels in theregion. Similarly, adenoid hyperplasis, or nasal obstruction leading tomouth breathing difficulty, can be treated in an adenoidectomy byseparating (e.g., resecting or ablating) the adenoid from the base ofthe nasopharynx.

Other pharyngeal disorders can be treated according to the presentinvention. For example, hypopharyngeal diverticulum involves smallpouches that form within the esophagus immediately above the esophagealopening. The sac of the pouch may be removed endoscopically according tothe present invention by introducing a rigid esophagoscope, andisolating the sac of the pouch. The cricopharyngeus muscle is thendivided, and the pouch is ablated according to the present invention.Tumors within the mouth and pharynx, such as hemangionmas,lymphangiomas, papillomas, lingual thyroid tumors, or malignant tumors,may also be removed according to the present invention.

Other procedures of the present invention include removal of vocal cordpolyps and lesions and partial or total laryngectomies. In the latterprocedure, the entire larynx is removed from the base of the tongue tothe trachea, if necessary with removal of parts of the tongue, thepharynx, the trachea and the thyroid gland.

Tracheal stenosis may also be treated according to the presentinvention. Acute and chronic stenoses within the wall of the trachea maycause coughing, cyanosis and choking.

The present invention is particularly useful in microendoscopicdiscectomy procedures, e.g., for decompressing a nerve root with alumbar discectomy. As shown in FIGS. 16-19, a percutaneous penetration270 is made in the patients' back 272 so that the superior lamina 274can be accessed. Typically, a small needle (not shown) is used initiallyto localize the disc space level, and a guidewire (not shown) isinserted and advanced under lateral fluoroscopy to the inferior edge ofthe lamina 274. Sequential cannulated dilators 276 are inserted over theguide wire and each other to provide a hole from the incision 220 to thelamina 274. The first dilator may be used to “palpate” the lamina 274,assuring proper location of its tip between the spinous process andfacet complex just above the inferior edge of the lamina 274. As shownin FIG. 17, a tubular retractor 278 is then passed over the largestdilator down to the lamina 274. The dilators 276 are removed,establishing an operating corridor within the tubular retractor 278.

As shown in FIG. 17, an endoscope 280 is then inserted into the tubularretractor 278 and a ring clamp 282 is used to secure the endoscope 280.Typically, the formation of the operating corridor within retractor 278requires the removal of soft tissue, muscle or other types of tissuethat were forced into this corridor as the dilators 276 and retractor278 were advanced down to the lamina 274. This tissue is usually removedwith mechanical instruments, such as pituitary rongeurs, curettes,graspers, cutters, drills, microdebriders and the like. Unfortunately,these mechanical instruments greatly lengthen and increase thecomplexity of the procedure. In addition, these instruments sever bloodvessels within this tissue, usually causing profuse bleeding thatobstructs the surgeon's view of the target site.

According to the present invention, an electrosurgical probe or catheter284 as described above is introduced into the operating corridor withinthe retractor 278 to remove the soft tissue, muscle and otherobstructions from this corridor so that the surgeon can easily accessand visualization the lamina 274. Once the surgeon has reached hasintroduced the probe 284, electrically conductive fluid 285 is deliveredthrough tube 233 and opening 237 to the tissue (see FIG. 3). The fluidflows past the return electrode 112 to the electrode terminals 104 atthe distal end of the shaft. The rate of fluid flow is controlled withvalve 17 (FIG. 2) such that the zone between the tissue and electrodesupport 102 is constantly immersed in the fluid. The power supply 28 isthen turned on and adjusted such that a high frequency voltagedifference is applied between electrode terminals 104 and returnelectrode 112. The electrically conductive fluid provides the conductionpath (see current flux lines) between electrode terminals 104 and thereturn electrode 112.

The high frequency voltage is sufficient to convert the electricallyconductive fluid (not shown) between the target tissue and electrodeterminal(s)104 into an ionized vapor layer or plasma (not shown). As aresult of the applied voltage difference between electrode terminal(s)104 and the target tissue (i.e., the voltage gradient across the plasmalayer), charged particles in the plasma (viz., electrons) areaccelerated towards the tissue. At sufficiently high voltagedifferences, these charged particles gain sufficient energy to causedissociation of the molecular bonds within tissue structures. Thismolecular dissociation is accompanied by the volumetric removal (i.e.,ablative sublimation) of tissue and the production of low molecularweight gases, such as oxygen, nitrogen, carbon dioxide, hydrogen andmethane. The short range of the accelerated charged particles within thetissue confines the molecular dissociation process to the surface layerto minimize damage and necrosis to the underlying tissue.

During the process, the gases will be aspirated through opening 209 andsuction tube 211 to a vacuum source. In addition, excess electricallyconductive fluid, and other fluids (e.g., blood) will be aspirated fromthe operating corridor to facilitate the surgeon's view. During ablationof the tissue, the residual heat generated by the current flux lines(typically less than 150° C.), will usually be sufficient to coagulateany severed blood vessels at the site. If not, the surgeon may switchthe power supply 28 into the coagulation mode by lowering the voltage toa level below the threshold for fluid vaporization, as discussed above.This simultaneous hemostasis results in less bleeding and facilitatesthe surgeon's ability to perform the procedure.

Another advantage of the present invention is the ability to preciselyablate soft tissue without causing necrosis or thermal damage to theunderlying and surrounding tissues, nerves or bone. In addition, thevoltage can be controlled so that the energy directed to the target siteis insufficient to ablate the lamina 274 so that the surgeon canliterally clean the tissue off the lamina 274, without ablating orotherwise effecting significant damage to the lamina.

Referring now to FIGS. 18 and 19, once the operating corridor issufficiently cleared, a laminotomy and medial facetectomy isaccomplished either with conventional techniques (e.g., Kerrison punchor a high speed drill) or with the electrosurgical probe 284 asdiscussed above. After the nerve root is identified, medical retractioncan be achieved with a retractor 288, or the present invention can beused to ablate with precision the disc. If necessary, epidural veins arecauterized either automatically or with the coagulation mode of thepresent invention. If an annulotomy is necessary, it can be accomplishedwith a microknife or the ablation mechanism of the present inventionwhile protecting the nerve root with the retractor 288. The herniateddisc 290 is then removed with a pituitary rongeur in a standard fashion,or once again through ablation as described above.

As shown in FIG. 19, the nucleus pulposis 290 often impinges on thespinal nerve 275, which results in back pain. In order to remove orablate the pulposis and relieve the pressure on the spinal nerve 275,the surgeon must operate extremely close to the nerve 275, which greatlyenhances the risk of nerve damage or destruction, particularly inendoscopic procedures. The present invention provides the ability toremove this spinal tissue without damaging the spinal nerve.

In another embodiment, the electrosurgical probe of the presentinvention can be used to ablate and/or contract soft tissue within thedisc 290 to allow the annulus 292 to repair itself to preventreoccurrence of this procedure. For tissue contraction, a sufficientvoltage difference is applied between the electrode terminals 104 andthe return electrode 112 to elevate the tissue temperature from normalbody temperatures (e.g., 37° C.) to temperatures in the range of 45° C.to 90° C., preferably in the range from 60° C. to 70° C., as discussedin detail above. This temperature elevation causes contraction of thecollagen connective fibers within the disc tissue so that the disc 290withdraws into the annulus 292.

The system and method of the present invention may also be useful toefficaciously ablate (i.e., disintegrate) cancer cells and tissuecontaining cancer cells, such as cancer on the surface of the epidermis,eye, colon, bladder, cervix, uterus and the like. The presentinvention's ability to completely disintegrate the target tissue can beadvantageous in this application because simply vaporizing andfragmenting cancerous tissue may lead to spreading of viable cancercells (i.e., seeding) to other portions of the patient's body or to thesurgical team in close proximity to the target tissue. In addition, thecancerous tissue can be removed to a precise depth while minimizingnecrosis of the underlying tissue.

Other modifications and variations can be made to disclose embodimentswithout departing from the subject invention as defined in the followingclaims. For example, it should be noted that the invention is notlimited to an electrode array comprising a plurality of electrodeterminals. The invention could utilize a plurality of return electrodes,e.g., in a bipolar array or the like. In addition, depending on otherconditions, such as the peak-to-peak voltage, electrode diameter, etc.,a single electrode terminal may be sufficient to contract collagentissue, ablate tissue, or the like.

In addition, the active and return electrodes may both be located on adistal tissue treatment surface adjacent to each other. The active andreturn electrodes may be located in active/return electrode pairs, orone or more return electrodes may be located on the distal tip togetherwith a plurality of electrically isolated electrode terminals. Theproximal return electrode may or may not be employed in theseembodiments. For example, if it is desired to maintain the current fluxlines around the distal tip of the probe, the proximal return electrodewill not be desired.

What is claimed is:
 1. A method for selectively treating body structures at a target comprising: positioning an electrode terminal in close proximity with a tissue structure adjacent to nerves fibers enclosed within an outer sheath so that the electrode terminal is brought into at least partial contact or close proximity with the tissue structure and the outer sheath; and applying high frequency voltage between the electrode terminal and a return electrode; during the applying step, removing at least a portion of the tissue structure in situ with the high frequency voltage without causing damage to the nerve fibers within the outer sheath.
 2. The method of claim 1 further comprising removing the tissue structure in situ while inhibiting impairment of nerve function of the nerve fibers closely adjacent to said tissue structure.
 3. The method of claim 1 further comprising applying sufficient voltage to the electrode terminal in the presence of electrically conducting fluid to vaporize at least a portion of the fluid between the electrode terminal and the tissue structure.
 4. The method of claim 3 wherein the nerve fibers comprises stronger molecular bonds than the tissue structure, the method further comprising accelerating charged particles from the vaporized fluid to the tissue to cause dissociation of the molecular bonds within the tissue structure, wherein the energy of the charged particles is insufficient to cause dissociation of the molecular bonds within the nerve fibers.
 5. The method of claim 4 wherein the tissue structure has a molecular bond strength of less than 4.5 eV and the nerve fibers have a molecular bond strength of greater than 5 eV.
 6. The method of claim 1 further comprising positioning the electrode terminal within electrically conductive fluid and positioning the return electrode within the electrically conductive fluid to generate a current flow path between the return electrode and the electrode terminal.
 7. The method of claim 1 wherein the electrode terminal comprises a single, active electrode at the distal end of a shaft.
 8. The method of claim 1 further comprising aspirating fluid adjacent to the tissue structure during the removal step.
 9. An apparatus for selectively applying electrical energy to a body structure at a target site, the apparatus comprising: an electrosurgical probe having a shaft with a proximal end portion, a distal end portion and an electrode terminal disposed near the distal end portion; a connector near the proximal end portion of the shaft for electrically coupling the electrode terminal to a high frequency power supply; a return electrode adapted to be electrically coupled to the high frequency power supply; and means for applying sufficient high frequency voltage between the electrode terminal and the return electrode to remove at least a portion of a tissue structure in situ without causing damage to nerve fibers adjacent to the tissue structure.
 10. The apparatus of claim 9 further comprising a fluid delivery element for delivering electrically conductive fluid to the electrode terminal and, wherein said means for applying sufficient high frequency voltage comprises means for vaporizing at least a portion of the electrically conductive fluid between the electrode terminal and the tissue structure.
 11. The apparatus of claim 10 wherein the nerve fibers are enclosed within an outer sheath comprising stronger molecular bonds than the tissue structure, the apparatus further comprising means for accelerating charged particles from the vaporized fluid to the tissue structure to cause dissociation of the molecular bonds within the tissue structure, wherein the energy of the charged particles is insufficient to cause dissociation of the molecular bonds within the outer sheath.
 12. The apparatus of claim 9 further comprising a fluid delivery element defining a fluid path in electrical contact with the return electrode and the electrode terminal to generate a current flow path between the return electrode and the electrode terminal.
 13. The apparatus of claim 9 wherein the distal end portion of the shaft is sized for delivery into a paranasal sinus.
 14. The apparatus of claim 9 wherein the return electrode forms a portion of the shaft.
 15. The apparatus of claim 9 wherein the electrode terminal comprises an electrode array disposed near the distal end portion of the shaft, the array including a plurality of electrically isolated electrode terminals disposed over a contact surface.
 16. The apparatus of claim 9 wherein the electrode terminal comprises a single active electrode disposed near the distal end portion of the shaft. 